Continuously variable electrically actuated flow control valve for high temperature applications

ABSTRACT

A continuously variable electrical actuator rotationally coupled to and thermally isolated from a butterfly valve. The butterfly valve may be used to modulate high temperature exhaust gas flow through an engine turbocharger. An electrical actuator provides a continuously variable output to an output shaft. The butterfly valve has its rotary position controlled by an input shaft. The input shaft and output shaft are rotationally coupled through minimum contact points to reduce heat transfer. The connection between input and output shafts also minimizes vibration transfer therebetween. An coupling tube coaxially interposed between the input and output shafts provides a thermal block to further reduce heat transfer. The input and outputs shafts are rotationally coupled to the intermediate shaft by torsion spring mechanisms to allow a limited range of axial translation for the input shaft. The torsion spring mechanisms are preloaded to prevent rotational hysteresis in the butterfly valve.

FIELD OF THE INVENTION

This invention relates generally to flow control valves and moreparticularly to continuously variable butterfly valves for applicationsin engines.

BACKGROUND OF THE INVENTION

There are a number of high temperature applications where fast andaccurate control over fluid flow is needed. One exemplary and verysignificant application is controlling the boost pressure provided by aturbocharger. Turbochargers affect the air fuel (A/F) ratio combusted inthe cylinders of modern internal combustion engines, which includesdiesel and natural gas engines. Turbochargers include a compressor forcompressing air and a turbine for driving the compressor. The turbineoperates off of the exhaust flow exiting the engine. To achieve the mostefficient engine performance, the boost pressure of the air deliveredinto the cylinders must be accurately controlled.

One way to obtain better control over the compressor boost pressure isto control the amount of exhaust flowing through the turbine. This canbe done by providing a controlled wastegate valve which closelyregulates or modulates the amount of exhaust flowing through theturbine. Design of the controlled wastegate valve must take intoconsideration the harsh environment in which the valve operates. Thewastegate valve may be subjected to exhaust gas temperatures of up to1400° F. Being in close proximity to the combustion chambers, thewastegate valve also must handle the vibration and heat transfer comingfrom the engine block.

There are known prior attempts of regulating the exhaust flow throughthe turbines of turbochargers using pneumatically controlled flowcontrol valves. A typical prior attempt includes the use of a pneumaticactuator for controlling the position of a swing valve or poppet valve.The swing or poppet valve regulates the flow of exhaust through anexhaust bypass in the engine turbocharger. While, pneumatic actuatorscan be configured to withstand the high temperature environment, theyprovide a slow response with a significant amount of rotationalhysteresis resulting from pressure differentials between the valve andthe pneumatic actuator. Furthermore, swing and poppet valves have veryhigh gain characteristics, making precise control impracticable. Thesefactors cause deficient control of the turbo boost pressure. Thisresults in inefficient control of the engine turbocharger and lowerefficiency for the combustion engine.

In cool temperature applications, such as throttling ambient temperatureair into an engine, there are known electrically actuated butterflyvalves. Such electrically actuated butterfly valves typically have asingle solid shaft which transfers the rotational output of anelectrical actuator to the butterfly valve. These electrical actuatorsare highly responsive which provides fast and accurate control of thebutterfly valve and the low temperature gas which flows therethrough.However, the shaft is an excellent conductor of heat and vibration whichwould cause overheating and/or failure of the electrical actuator ifapplied to high temperature applications, such as a wastegate flowcontrol valve for regulating exhaust flow to a turbocharger for example.

There are also known attempts at providing electrically actuatedbutterfly valves for exhaust braking. For example, U.S. Pat. No.2,753,147, to Welge, illustrates an electrically actuated on/offbutterfly valve for building backpressure against the engine pistons toslow the vehicle when the vehicle is traveling down a steep slope.However, the engine braking valve in Welge would not be suitable forcontrolling turbo boost pressure in an engine. Welge discloses an on/offtype valve that is not continuously variable. Such on/off type valves donot provide the control, responsiveness or accuracy necessary for thedesired control of turbo boost pressure. Furthermore, the output shaftof the electrical actuator is disposed along a separate axis spacedparallel to the input shaft of the butterfly valve. Rotation istransferred from the output shaft to the input shaft by a spring, rollerand track mechanism which causes the input and output shafts to rotatein opposite directions. This connection between input and output shaftincreases the complexity of the valve and allows rotational play betweenshafts which in turn would decrease the responsiveness and control ofthe butterfly valve.

Yet, another problem with Welge is that it does not appear to be adaptedfor the harsher environmental conditions necessary for controllingexhaust flow through an engine turbocharger. In Welge, the butterflyvalve is adapted to be mounted between the outlet of the exhaustmanifold and the inlet of the exhaust line, which can be furtherdownstream from the engine combustion chamber as compared with thetypical location of the bypass in an engine turbocharger. Thisdownstream location is a less harsh environment in terms of temperatureand vibration as compared with a typical turbocharger bypass. Andtherefore it does not suffer from the problems to which the instantinvention is directed.

SUMMARY OF THE INVENTION

It is therefore the general aim of the present invention to achievebetter control over fluid flow in high temperature applications.

It is another aim of the present invention to provide an electricallycontrolled continuously variable butterfly valve for high temperatureapplications.

It is a more specific aim of the present invention to provide anelectrically controlled continuously variable butterfly valve adaptedfor high temperature operation in internal combustion and/or turbineengine applications.

In that regard, it is another aim of the present invention to improvecontrol of turbochargers in internal combustion engines.

According to another aspect, an objective of the present invention toutilize electronic control or electrically driven actuation incontrolling engine turbochargers.

It is therefore an object of the present invention to minimize heattransfer between a butterfly valve and a continuously variableelectrical actuator.

A related object is to accommodate thermal expansion and contraction ofthe butterfly valve relative to the actuator.

It is another object of the present invention to provide an electricallyactuated butterfly valve that can tolerate a substantial amount ofvibration.

It is a specific object of the present invention, in a particularembodiment, to provide an electrically controlled butterfly valve thatcan regulate a gas flow having a maximum temperature of approximately1400° F.

It is another specific object of the present invention to improve thespeed and accuracy of controlling exhaust gas flow through engineturbochargers.

It is another specific object of the present invention to minimizerotational hysteresis in the flow control valve which regulates exhaustgas flow through an engine turbocharger during normal operation thereof.

It is another object of the present invention to provide a compactelectrically actuated butterfly valve for high temperature applicationsthat requires only passive cooling.

It is therefore a feature of the present invention to provide anelectrically actuated flow control valve for accurate control of fluidflow in high temperature applications. According to this feature, anelectrical actuator includes an output shaft that has a rotary positionproportionally related to electric signals applied to the electricalactuator. The flow control valve includes an input shaft coupled to amovable valve member to regulate fluid flow through a fluid passage. Theinput shaft and output shaft are coaxially aligned and rotationallycoupled by a coupling tube for direct transfer of rotary movement fromthe electrical actuator to the flow control valve. The coupling tubeserves as a thermal block between the input and output shafts. Couplingmeans joins the coupling tube to the respective input and output shaftsrestricting heat transfer therethrough.

It is an aspect of the present invention that the flow control valve isa butterfly valve that includes an annular plate mounted in an annularfluid passage for regulating flow therethrough. The butterfly valveprovides far better control over fluid flow through the fluid passage asgenerally compared to swing or poppet type flow control valves.

It is another feature of the present invention to provide anelectrically actuated butterfly valve for modulating high temperaturefluid flow in engines. According to this feature, a preferred embodimentprovides an electrical actuator having a continuously variablerotational output on an output shaft and a butterfly valve with an inputshaft that is connected to the output shaft to receive the continuouslyvariable rotational output. An intermediate shaft or coupling tubecouples the input and output shafts while providing a thermal blocktherebetween.

It is a related feature that the electrical actuator and butterfly valveare fixed by an intermediate housing to provide an integral electricallyactuated butterfly valve component. It is a further aspect that thehousing includes rows of compliance slots which serve also thermalresistors to reduce heat transfer between the butterfly valve andelectrical actuator while providing axial and angular compliancetherebetween.

It is another aspect of the present invention that the connectionbetween input and output shafts allows for angular and axial translationtherebetween. This allows for small angular and axial displacements andmisalignments between the electrical actuator and the butterfly valve,which can be caused by thermal expansion or contraction and vibrationsbetween the butterfly valve and the electrical actuator.

It is another aspect of the present invention to provide asealing/thrust mechanism on the input shaft of the butterfly valve tostabilize the position of annular valve plate with respect to the fluidpassage. The sealing/thrust mechanism reduces axial translations of theinput shaft to prevent the annular valve plate from scraping or bindingwith the walls of the fluid passage.

It is another aspect of the present invention to provide torsion springmechanisms to rotationally couple the intermediate coupling tube to theinput and output shafts. The torsion spring mechanisms have axial andangular flexibility to allow angular and axial translations. Inaccordance with a specific object, the torsion springs are preloaded toprovide a rotational spring force or torque greater than that which theelectrical actuator or butterfly valve will exert during normaloperation to eliminate substantially all rotational hysteresis andbacklash between the input and output shafts.

It is another feature of the present invention to provide anelectrically controlled butterfly valve that improves the control ofboost pressure provided by an engine turbocharger. Accordingly, abutterfly valve is mounted in an exhaust manifold of an engine tomodulate exhaust flow through the turbine of an engine turbocharger. Therotary position of the butterfly valve is controlled by a continuouslyvariable electrical actuator. Appropriate connecting means connect therotational output of the actuator to the butterfly valve for accurateand fast control of the butterfly valve while thermally isolating theelectrical actuator from high temperature fluid that flows through thebutterfly valve.

It is another feature of the present invention to provide a method ofmodulating fluid flow through an engine turbocharger using a butterflyvalve. The method includes the steps of producing a continuouslyvariable rotational output using an electrical actuator, closely anddirectly coupling the actuator output to the butterfly valve whilethermally isolating the electrical actuator from the butterfly valve andallowing a range of axial and angular translation between the butterflyvalve/input shaft and electrical actuator/output shaft.

These and other objects and advantages of the invention will become moreapparent from the following detailed description when taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an electrically controlled butterflyvalve according to a preferred embodiment of the present invention.

FIG. 2 is a cross-sectional view taken about line 2--2 of theelectrically controlled butterfly valve of FIG. 1.

FIG. 3 is an enlarged fragmentary view of the electrically controlledbutterfly valve of FIG. 2 identified by the dashed circle 3.

FIG. 4 is a perspective view of the electrically controlled butterflyvalve of FIG. 1 with the outer housing tube removed.

FIG. 5 is a schematic illustration of an electrically controlledbutterfly valve incorporated in an engine environment according to apreferred embodiment of the present invention.

While the invention is susceptible of various modifications andalternative constructions, certain illustrative embodiments thereof havebeen shown in the drawings and will be described below in detail. Itshould be understood, however, that there is no intention to limit theinvention to the specific forms disclosed, but on the contrary, theintention is to cover all modifications, alternative constructions andequivalents falling within the spirit and scope of the invention asdefined by the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

For purposes of illustration and referring to FIG. 1, a preferredembodiment of the present invention has been depicted as an electricallycontrolled butterfly valve apparatus 20 for high temperatureapplications. Although the preferred embodiment will be described asparticularly adapted for controlling exhaust gas flow which may have atemperature of up to about 1400° F., it should be understood from theoutset that the preferred embodiment may be adapted for controllingfluid flow in other high temperature engine applications and/or inassociation with other applications that need thermal isolation betweena valve and an electrical actuator. These broader aspects are consideredto be part of the present invention, and are covered by certain of thebroader claims appended hereto.

In accordance with the aim of achieving better control of fluid flow inhigh temperature applications, the preferred embodiment of the presentinvention generally includes an electrical actuator 22 that has acontinuously variable output for varying the rotary position of abutterfly valve 24 or other suitable flow control valve. The butterflyvalve 24 includes a generally cylindrical valve body 26, which can bestainless steel or other suitable material, that defines a cylindricalfluid passage 28 or other suitable annular shaped passage for passinghigh temperature exhaust gas. As used herein, the term annular is meantto include elliptical, oval, circular and any other acceptable curveshape. Referring now to FIG. 2, the valve body 26 includes a drivereceiving/mounting portion 30 that extends generally perpendicular tothe fluid passage 28. Extending across the valve body 26 and through thedrive receiving portion is a cylindrical bore 32, which extendsperpendicularly across the fluid passage 28 to include diametricallyopposed portions 32a, 32b.

A solid input shaft 34 is mounted in the bore 32 for rotation relativeto the valve body 26. The input shaft 34 extends through bothdiametrically opposed bore portions 32a, 32b and projects out from thedrive mounting/receiving portion 30 for receiving the continuouslyvariable rotational output from the electrical actuator 22. The inputshaft 34 is journalled between a pair of heat resistant carbon bearings36 so that the input shaft 34 rotates freely relative to the valve body26. An elliptical valve plate 38 or other appropriate annular shapedplate is rigidly fixed to the input shaft 34 by a pair of fasteners 40and closely fitted in the fluid passage 28 for regulating exhaust gasflow through the fluid passage 28. As shown in a fully closed positionin FIGS. 1-2, 4, the annular valve plate 38 is aligned to be generallyconcentric with the fluid passage 28.

The electrical actuator 22 produces the continuously variable outputthat is directly coupled to the input shaft 34 for fast, accurate andprecise control of the butterfly valve 24 and thereby of the exhaust gasflow through the fluid passage 28. The electrical actuator generallyincludes an electrical input line 42 for receiving electric signals andan output shaft 44 that is driven to a rotational position which isproportionally related to the electric input signals. In the preferredembodiment, the electrical actuator 22 is illustrated as a limited angletorquer (LAT) which converts a 4-20 mA input current to a proportionallyrelated rotary output position of the output shaft 44. As shown in thedrawings, the electrical actuator 22 includes an outer casing 46 thatcontains an inner stator assembly 48, and has a coil assembly 50connected to the electrical input line 42. The output shaft 44 includesa permanent magnet armature 52 which is responsive to current applied inthe coil 50. The electrical actuator 22 also includes a bearing housing54 fastened to the stator 48. The output shaft 44 is journalled by apair of steel ball bearings sets 56 in the bearing housing 54, andprojects out of the bearing housing 54. In accordance with a particularaspect of the present invention, it is seen that the input and outputshafts 34, 44 are coaxially aligned.

In keeping with the aims and objectives relating to accurate control ofthe butterfly valve position, the input and output shafts 34, 44, arerotationally coupled to directly transfer the continuously variablerotational output of the electrical actuator 22 to the butterfly valve24. In the preferred embodiment, a change in rotary position of theoutput shaft 44 simultaneously and correspondingly modifies the rotaryposition of the input shaft 34 and therefore the valve plate 38.Accordingly, an intermediate coupling tube 58, or other intermediateshaft joins the input and output shafts 34, 44. The intermediatecoupling tube 58 provides open ends 60, 61 that readily receivecoaxially opposed shaft ends 63, 64 of the output shaft 44 and inputshaft 34, respectively.

To rotationally couple the input and output shafts 34, 44, and referringnow to FIGS. 2 and 4, the intermediate coupling tube 58 is connected tothe input and output shafts 34, 44 by a pair of torsion springmechanisms generally indicated at 66 and 68, or other suitable couplingmeans. In the preferred embodiment, each torsion spring mechanismincludes a roll pin 70, or other rigid radially extending member, and atorsion spring 72. The roll pins 70 are pressed in corresponding holes74 formed in the ends 63, 64 of the respective shafts 33, 44 and fixedto the shafts thereby. The ends of the roll pins 70 ride axially alongaxially extending slots 78 formed at the open ends 60, 61 of the tube.Each torsion spring 72 is fitted over the coupling tube 58 and has anaxially extending outward end 80 which cradles and engages a roll pin 70through a tangential contact point or line. Each torsion spring 72 alsoincludes an inward end 82 that engages the intermediate coupling tube58, in this case the inward ends 82 are bent and fitted into the axialslots 78 of the coupling tube 58. The torsion spring mechanisms 66, 68prevent rotational backlash between the input shaft 34 and output shaft44. To provide this, each roll pin 70 is loaded between the torsionspring outer end 80 and one edge of the axial slot 78.

To provide direct response without backlash and without rotationalhysteresis between the electrical actuator 22 and butterfly valve 24,the torsion springs 72 are preloaded to provide a rotational biasgreater than the torque that the electrical actuator 22 and butterflyvalve 24 will exert on the coupling tube 58 during normal operation.This prevents rotational hysteresis in the butterfly valve 24 andprovides an exact response in the butterfly valve plate 38, which inturn, provides better control over the exhaust flow through the fluidpassage 28.

In accordance with a feature of the present invention and referring toFIGS. 1 and 2, the electrical actuator 22 and butterfly valve 24 arebuilt into one integral assembly. Accordingly, an outer housing tube 86fixes the valve body 26 to the bearing housing 54 of the electricalactuator 22 to prevent rotation therebetween. In the preferredembodiment, the outer housing tube 86 contains the intermediate couplingtube 58 and projecting ends 63, 64 of the input and output shafts 34,44. The outer housing tube 86 is fastened between the electricalactuator 22 and valve body 26 by sockethead cap screws 88, or other suchsuitable fasteners. The housing tube 86 also includes a plurality ofaccess openings 89 in close proximity to the drive receiving/mountingportion 30 of the valve body 26 to allow access for disconnecting andconnecting the torsion spring mechanism 68. Although a housing 86 isprovided in the preferred embodiment, the outer housing tube 86 could beremoved (as shown in FIG. 3) to the extent that the butterfly valve 24and electrical actuator are rigidly fixed to external components.

In operation, high temperature exhaust gas or other fluid can becontinuously applied to the fluid passage 28. The electrical currenttransmitted through line 42 to the electrical actuator 22 is controlledto selectively position the valve plate 38 as desired. In a preferredembodiment, the electrical actuator 22 is continuously variable so thatthe valve plate 38 may be selectively positioned and selectively held inany position between the fully open and fully closed positions. Theposition of the valve plate 38 may be updated as desired so that thevalve plate 38 modulates flow. The speed at which flow is modulateddepends on the particular application of the butterfly valve 24 and therate at which the electrical actuator 22 responds to electrical inputsignals.

In a preferred embodiment, the butterfly valve 24 is adapted to passexhaust gas or other high temperature fluid that can have a temperatureof up to approximately 1400° F., while the electrical actuator 22 has anupper temperature limit of approximately 212° F. before failure ormalfunction. In accordance with the invention, the electrical actuatoris protected from this adverse environment by limiting heat transferalong the control and mounting mechanism. As shown herein, the controlor drive mechanism which transfers continuously variable rotationaloutput from the electrical actuator 22 to the butterfly valve 24 isbroken into separate thermally isolated drive shafts (input and outputshafts 34, 44) with the coupling tube 58, an intermediate shaft or otherthermal block therebetween. The contact areas between the coupling tube58 and the drive shafts 34, 44 are limited to provide at least one andpreferably several thermal barriers which restrict heat transfertherebetween sufficient to prevent thermal damage to the electricalactuator 22 for the particular thermal fluid application. In thepreferred embodiment, the inner diameter of the end openings of thecoupling tube 58 are sized sufficiently larger than the respective outerdiameter of the input shaft 34 and output shaft 44 to provide aninsulating gap and minimize contact between the coupling tube 58 and theinput and output shafts 34, 44. Each insulating gap between the tube 58and the shafts 34, 44 serves as a primary thermal barrier preventingoverheating of the electrical actuator. Moreover, the input and outputshafts 34, 44 have only a small end portion slidably fitted into thecoupling tube 58 to limit heat transfer therebetween.

Heat restriction and thermal barriers are also provided by the torsionspring mechanisms 66, 68 or other such suitable coupling means thatjoins the coupling tube 58 to the input and output shafts 34, 44. Thetorsion spring mechanisms 66, 68 or other coupling means minimizes themetallic contact points and/or metallic cross-sectional metallic areasbetween the input and output shafts. As can be seen best in FIG. 2 ofthe preferred embodiment, the torsion springs 72 provide minimummetallic contact points through tangential or other minimum contact withthe roll pin 70. The roll pins 70 also only have a metallic tangentialcontact line to the wall edges of the respective slots 78.

A preferred embodiment also uses metal materials, or other durablematerials that have low thermal conductivity to further reduce heattransfer. Accordingly, the materials used for the intermediate couplingtube 58, input shaft 34 and outer housing tube 86 are preferably formedof stainless steel material, or other low thermally conductive rigidmaterial. The valve plate 38 may be formed from Inconel type steel whichalso has heat resistant qualities.

Another aspect of a preferred embodiment includes the use of radiallydefined compliance slots 90 on the outer housing tube 86, as may be seenbest in FIG. 2. Compliance slots 90 are aligned in adjacent rows 92A,92B, 92C formed in out-of-phase alignment with one another. As seenthere are multiple rows 92A, 92B, 92C of compliance slots 90, each row92A, 92B, 92C being geometrically rotated by 1200 or other appropriateangle with respect to adjacent rows 92A, 92B, 92C. These complianceslots 90 serve as thermal resistors because the cross sectional area ofthe outer housing tube 86 is greatly reduced, while the effectivethermal conductive length of the outer housing tube 86 is increased. Theaccess orifices 89 also increase the thermal resistance of the outerhousing tube 86.

In practicing the preferred embodiment, the electrical actuator isadapted to mount in bracketing (not shown) while the butterfly valve 24is mounted on piping conduit (shown schematically in FIG. 5). Theinstallation of butterfly valve 24 and electrical actuator arepreferably done at room temperature. However, during operation of theelectrically controlled butterfly apparatus 20, a significanttemperature differential exists between the electrical actuator 22 andthe butterfly valve 24. Such temperature differentials can cause axialand angular thermal displacements and misalignments between thebutterfly valve 24 and the electrical actuator 22. In addition, theelectrically controlled butterfly valve apparatus 20 is adapted for anengine environment (as shown in FIG. 5), and engine vibrations can addadditional stress to the axial and angular thermal displacements.

In accordance with the objective of accommodating thermal expansion inthe butterfly valve, the preferred embodiment provides a limited rangeof axial and angular translations of the input shaft 34 relative to theoutput shaft 44. So that it will be clear, as used herein, angulartranslations (not to be confused with rotational backlash which thepreferred embodiment eliminates) refers to misalignments between theaxis of the input shaft 44 and the axis of the output shaft 34. In thepreferred embodiment, the end openings of the coupling tube 58 are sizedlarge enough to permit approximately a 2° angle of angular misalignmentbetween the axes of the input and output shafts 34, 44. The roll pins 70axially ride along the axial slots 78 so that the input shaft 34 canaxially translate through a range of positions in the open end 61without creating axial stresses. Due to the resilient nature of thetorsion springs 72, the connection joints between the intermediatecoupling tube 58 and the shafts 34, 44 have a range of flexibility toaccommodate both axial and angular translations. The out-of-phasecompliance slots 90 also provide a limited amount of flexible compliancein the outer housing tube 86 to reduce stresses when small angular andaxial displacements occur between the electrical actuator and thebutterfly valve 24.

In accordance with another aspect of the present invention and referringto FIGS. 2 and 3, the preferred embodiment provides a sealing/thrustmechanism generally indicated at 96 that eliminates axial translation ofthe input shaft 34 to stabilize the axial position of the annular valveplate 38 relative to the fluid passage 28. The sealing/thrust mechanism96 reduces vibrations and large axial translations of the input shaft 34which could cause the valve plate 38 to bind or scrape against the wallsof the fluid passage 28. The sealing/thrust mechanism 96 of thepreferred embodiment is formed in an enlarged portion 98 of thecylindrical bore 32. The sealing/thrust mechanism 96 includes an innersleeve 100 which rides slidably over the input shaft 34 and an outersleeve 102 that is axially fastened to the valve body 26 and is disposedconcentrically over the inner sleeve 100. The outer sleeve 102 and theinner sleeve 100 form a spring chamber 104. A spring 106 is coaxiallydisposed in the spring chamber to seat the inner sleeve 100 against aseal washer 110. The input shaft 34 also defines a shoulder 108 whichreceives the axial spring 106 force to stabilize the position of theinput shaft 34 and thereby the annular valve plate 38. Compressedbetween the shoulder 108 and the inner sleeve 100 is a temperatureresistant carbon seal washer 110 which acts as a seal to prevent fluidleakage through the bore 32.

Turning to FIG. 5, an exemplary and very significant application of thepresent invention is schematically illustrated. In accordance with theaim of improving control over engine turbochargers, the electricallyactuated butterfly valve apparatus 20 is configured as a wastegate influid communication with a turbocharger 200 of an internal combustionengine 202. The internal combustion engine has a compressed air inletconduit 204 leading to the combustion chambers of the engine 202 and anexhaust gas outlet conduit 206 for discharge. The turbocharger 200includes a compressor 208 which compresses air to the inlet conduit 204and a turbine 210 which powers the compressor 208. The turbine 210 isdriven by exhaust gas flow through the outlet conduit 206. To controlthe power of the turbine 210 and thereby the air/fuel ratio in thecombustion chambers of the engine 202, there is provided an exhaust gasbypass line 212 which is controlled by the electrically controlledbutterfly apparatus 20 that is shown in FIGS. 1-3. The bypass 212 isdisposed in fluidic parallel with the outlet conduit 206 to divertexhaust gas flowing to the turbine 210. This controls the operatingspeed of the compressor 208 and thereby the boost pressure provided bythe turbocharger 200 to the engine 202. The exhaust gas flow through thebypass 212 may have temperatures of up to approximately 1400° F.depending upon the particular type of engine.

Although one high temperature application has been shown in FIG. 5, itwill be understood that the present invention can be used in a number ofapplications where thermal isolation of the electrical actuator 22 isneeded or where significant range of angular and axial displacements mayoccur between the electrical actuator 22 and butterfly valve 24. Theelectrically controlled butterfly valve apparatus 20 has thermaladvantages in any application where the fluid being controlled isgreater than the temperature limit of the electrical actuator 22,particularly where fluid temperatures through the butterfly approach100° F. more than the temperature limit of the electrical actuator(which as was mentioned, is limited to about 212° F.), when thepossibility of overheating the electrical actuator 22 with only a singleshaft becomes very significant. For example, this valve may also be usedin controlling compressor 208 bypass and/or turbine 210 bleed operationsin internal combustion engines 202. In applications such as controllingcompressor 208 bypass, the temperature is much less than 1400° F.,although compressed air has a higher temperature than ambient air. Insuch lower high temperature applications, it will be appreciated tothose skilled in the art that the input and output shafts 34, 44 may bedirectly coupled through one torsion spring mechanism or otherrotational coupler thereby eliminating the intermediate coupling tube.The electrically controlled butterfly valve apparatus 20 may also beused in turbine engine applications (not to be confused withturbochargers of internal combustion engines) for modulating fluid flowtherein or possibly other such situations which desire an accurate andresponsive valve to operate with high temperature fluids.

What is claimed is:
 1. An apparatus for controlling fluid flowcomprising:a flow control valve having a valve body, a movable valvemember, and an input shaft, the valve body defining a fluid passage, themovable valve member being coupled to the input shaft and rotatable inthe fluid passage for regulating fluid flow through the fluid passage;an electrical actuator having an output shaft and an electrical input,the rotary position of the output shaft being proportionally related toelectric signals applied to the electrical input, the output shaft beingcoaxially aligned with the input shaft; a rotatable coupling tubecoaxial with the input and output shafts; and coupling means joining thetube with the shafts for restricting heat transfer from the butterflyvalve to the electrical actuator.
 2. The apparatus for controlling fluidflow as in claim 1 wherein the coupling means provides minimum metalliccontact points between the coupling tube and the shafts to thermallyisolate the electrical actuator from the flow control valve sufficientto prevent thermal damage to the electrical actuator.
 3. An apparatus asin claim 2 wherein the coupling means eliminates substantially allrotational hysteresis between the input and output shafts.
 4. Anapparatus as in claim 1 wherein the coupling means provides a range ofaxial translation relative to the output shaft to allow for thermalexpansion and contraction of the flow control valve.
 5. An apparatus asin claim 4 further including a sealing/thrust mechanism connected to thevalve body, the sealing/thrust mechanism engaging the input shaft toreduce axial translation of the input shaft so that the annular platemaintains a substantially constant axial position inside the valve body.6. An apparatus as in claim 1 wherein the coupling tube defines firstand second ends slidably receiving the respective input and outputshafts, the first and second ends being rotationally coupled to therespective input and output shafts by torsion spring mechanisms.
 7. Anapparatus as in claim 1 further including a housing tube surrounding thecoupling tube and having flanges at each end thereof respectively fixedto the electrical actuator and the valve body for preventing rotationtherebetween.
 8. An apparatus as in claim 1 wherein the flow controlvalve is mounted in close proximity to an engine in fluid communicationwith an engine turbocharger for regulating boost pressure provided bythe engine turbocharger.
 9. An apparatus as in claim 1 wherein the flowcontrol valve is a butterfly valve, the fluid passage is cylindricallyshaped and the valve member is an annularly shaped plate.
 10. Anapparatus for modulating the flow of high temperature fluid comprising:abutterfly valve having a valve body, an annular valve plate, and aninput shaft, the valve body defining a fluid passage for interpositionalong a fluid conduit, the annular valve plate being coupled to theinput shaft and mounted for continuously variable rotation in the fluidpassage; an electrical actuator having a continuously variablerotational output on an output shaft, a rotatable coupling tube joiningthe output shaft and the input shaft to transfer the continuouslyvariable output from the electrical actuator to the butterfly valve, thecoupling tube having at least one thermal barrier imposed therein toreduce heat transfer between the butterfly valve and the electricalactuator; and a housing fixing the valve body with the electricalactuator to prevent rotation between the valve body and the electricalactuator.
 11. An apparatus as in claim 10 wherein the electricalactuator has a temperature limit, the electrical actuator being subjectto damage when temperatures in the output shaft of the electricalactuator are above the temperature limit, the fluid passage adapted topass a thermal fluid having a temperature more than 100° F. above saidtemperature limit, the coupling tube prevents damage to the electricalactuator during a continuous application of said thermal fluid to thefluid passage.
 12. An apparatus as in claim 10 further including a pairof torsion spring mechanisms, one at each end of the coupling tubelinking the input and output shafts to the coupling tube, the torsionspring mechanisms being preloaded to a torque greater than that whichthe butterfly valve and electrical actuator will exert during operationto thereby minimize rotational hysteresis between input and outputshafts.
 13. An apparatus as in claim 10 wherein the input and outputshafts are slidably fitted into respective ends of the coupling tube toallow a limited range of axial and angular translation between the inputand output shafts to allow for thermal expansion in butterfly valveduring application of high temperature fluid through the fluid passage.14. An apparatus as in claim 13 further comprising a sealing/thrustmechanism on the input shaft for reducing axial translation of the inputshaft to maintain relatively constant the axial position of the annularvalve plate relative to the valve body.
 15. An apparatus as in claim 10wherein at least one thermal barrier is an insulating gap providingminimum contact between the coupling tube and a selected one of theinput and output shafts.
 16. An apparatus as in claim 10 wherein thecoupling tube has first and second ends slidably receiving the input andoutput shafts, respectively, the first and second ends have minimumcontact with the input and output shafts to provide first and secondprimary thermal barriers, respectively.
 17. The apparatus as in claim 16wherein the first and second ends define axially extending first andsecond slots, the input shaft providing a first rigid member extendingradially into the first slot, the output shaft providing a second rigidmember extending radially into the second slot, third and fourth thermalbarriers disposed between the rigid members and the slots, respectively.18. An apparatus as in claim 10, wherein the housing is an outer tubesurrounding the coupling tube, the input shaft and the output shaft, theouter tube defines a plurality of apertures selectively arranged toprovide increased thermal resistance.
 19. An apparatus as in claim 11wherein the butterfly valve continuously passes a fluid having atemperature of approximately 1400° F. without damage to the electricalactuator.
 20. An apparatus as in claim 10 wherein the butterfly valve isconnected to an exhaust manifold of an internal combustion engine tomodulate exhaust gas flow through an engine turbocharger.
 21. Anapparatus for modulating the flow of high temperature fluid,comprising;a butterfly valve having a valve body, an annular valveplate, and an input shaft, the valve body defining a fluid passage, theannular valve plate being coupled to the input shaft and mounted forcontinuously variable rotation in the fluid passage for modulating theflow of high temperature fluid through the fluid passage; an electricalactuator having an electric input and an output shaft for continuouslyvariable movement, the rotary position of the output shaft beingproportionally related to the electric input; a housing fixing the valvebody with the electrical actuator to coaxially align the input andoutput shafts; and an intermediate rotatable shaft interposed betweenthe input and output shafts, the intermediate shaft joined to the inputand output shafts to transfer continuously variable movement from theelectrical actuator to the butterfly valve while thermally isolating theelectrical actuator from the butterfly valve, the input shaft having alimited range of axial and angular translation relative to the outputshaft to allow for thermal expansion of the butterfly valve.
 22. Anapparatus as in claim 21 wherein the intermediate shaft is a tubecoaxially interposed between the input and output shafts, the input andoutput shafts slidably fitting into respective first and second ends ofthe coupling tube.
 23. An apparatus as in claim 22, wherein the tubedefines first and second axially extending slots at the first and secondends, respectively, the output shaft providing a first member slidablyfitted in the first axially extending slot, the input shaft providing asecond member slidably fitted in the second axially extending slot. 24.An apparatus as in claim 23 further comprising first and second torsionsprings, the first torsion spring fixed to the tube and engaging thefirst member, the second torsion spring fixed to the tube and engagingthe second member.
 25. An apparatus as in claim 24 wherein said firstand second torsion springs are preloaded to a torque greater than thetorque exerted by either of the input or output shafts during normaloperation of the butterfly valve to thereby minimizing rotationalhysteresis between the output shaft and input shaft.
 26. An apparatus asin claim 21 further comprising carbon bearings carried by the valvebody, the input shaft being journalled in carbon bearings.
 27. Anapparatus as in claim 21, further including a sealing/thrust mechanismconnected to the valve body and engaging the input shaft to reduce axialtranslation of the input shaft so that the annular plate maintains asubstantially constant position inside the valve body.
 28. An apparatusas in claim 27 wherein said sealing/thrust mechanism comprises an innersleeve, an outer sleeve and a spring, and wherein the input shaftprovides a shoulder, the inner sleeve being slidably positioned over theinput shaft, the outer sleeve axially fixed to the valve body andpositioned over the inner sleeve to form an annular chamber, the springbeing coaxially mounted in the annular chamber to urge the inner sleeveagainst the shoulder.
 29. An apparatus as in claim 21 wherein thehousing is tube shaped and defines a plurality of compliance slotsaligned radially about the housing in rows, the rows being aligned in anout-of-phase relationship with one another.
 30. An electrically actuatedbutterfly valve for modulating high temperature fluid, comprising:acontinuously variable electrical actuator having a continuously variableelectrical output on an output shaft; a butterfly valve comprising avalve body, an input shaft axially aligned with the output shaft, and anannular valve plate, the annular valve plate mounted to the input shaftfor rotation relative to the valve body, the valve body defining a flowpassage in which the annular valve plate is rotatable for regulatingflow through the flow passage; a housing securing the electricalactuator to the valve body; and means for joining the first and secondshafts to position the annular valve plate in response to thecontinuously variable output, said joining means providing a thermalbarrier including at least one minimum contact to prevent transfer ofheat from the butterfly valve to the electrical actuator along the inputand output shafts.
 31. The electrically actuated butterfly valve ofclaim 30 wherein said joining means comprises a rotatable tube axiallyinterposed between the input and output shafts, the input and outputshafts inserted into and connected to the respective first and secondends of the coupling tube.
 32. The electrically actuated butterfly valveof claim 31, wherein the tube defines first and second axially extendingslots at the first and second ends, respectively, the output shaftproviding a first projecting member slidably fitted in the first axiallyextending slot, the input shaft providing a second projecting memberslidably fitted in the second axially extending slot.
 33. Theelectrically actuated butterfly valve of claim 32 further comprisingfirst and second torsion springs disposed coaxially over the shaft andthe tube, the first torsion spring engaging the first projecting memberand biasing the tube in a first rotational direction, the second torsionspring engaging the second projecting member and biasing the tube in asecond rotational direction.
 34. The electrically actuated butterflyvalve of claim 33 wherein said first and second torsion springs arepreloaded to a torque greater than the torque exerted by either of theinput or output shafts during normal operation of the butterfly valve tothereby eliminate all rotational hysteresis between the output shaft andinput shaft.
 35. The electrically actuated butterfly valve of claim 34,further including a sealing/thrust mechanism connected to the valve bodyand engaging the input shaft to reduce axial translation of the inputshaft so that the annular plate maintains a substantially constantposition inside the valve body.
 36. The electrically actuated butterflyvalve of claim 35 wherein said sealing/thrust mechanism comprises aninner sleeve, an outer sleeve and a spring, and wherein the input shaftprovides a shoulder, the inner sleeve being slidably positioned over theinput shaft, the outer sleeve axially fixed to the valve body andpositioned over the inner sleeve to form an annular chamber, the springbeing coaxially mounted in the annular chamber to urge the inner sleeveagainst the shoulder.
 37. An apparatus as in claim 30 wherein thehousing is tubular and defines a plurality of compliance slots alignedradially about the housing in rows, the rows being aligned in anout-of-phase relationship with one another.
 38. An electrically actuatedbutterfly valve for modulating high temperature fluid, comprising:acontinuously variable electrical actuator having a continuously variableelectrical output on an output shaft; a butterfly valve comprising anvalve body, an input shaft axially aligned with the output shaft, and anannular valve plate, the annular valve plate mounted to the input shaftfor rotation relative to the valve body, the valve body defining a flowpassage in which the annular valve plate is rotatable for regulatingflow through the flow passage; a housing securing the electricalactuator to the valve body; and wherein the input shaft and the outputshaft are joined through at least one minimum contact to provide athermal barrier between the butterfly valve and the electrical actuator.39. The electrically actuated butterfly valve of claim 38 wherein theinput shaft is fixed relative to the output shaft by a spring meansduring electrical actuation of the butterfly valve, thereby ensuring norotational hysteresis between the input shaft and the output shaft. 40.The electrically actuated butterfly valve of claim 38 wherein there isat least two minimum contacts.